Wear-resistant spouts for metallurgical vessels

ABSTRACT

A wear-resistant spout for metallurgical vessles in which a pore-free material which exhibits high resistance to erosion by the molten contents of the vessel is utilized to line the passageway in said spout, a particularly preferred material is melt-cast corundum.

Apr. 2, 1974 United States Patent Mantey et a1.

[54] WEAR-RESISTANT SPOUTS FOR 164/337; 266/38; 106/50, 57, 62, 65

METALLURGICAL VESSELS [56] References Cited UNITED STATES PATENTS [75] Inventors: Paul Gerhard Mantey; Eberhard Knorr, both of Amberg, Germany Eisenwerke Gesellschait,

[73] Assignee: 3,511,261 5/1970 Bick et 266/38 X Maximilianshutte m.b.H., Sulzbach Rosenberg, Germany Dec. 29, 1972 Primary Examiner-Gerald A. Dost Attorney, Agent, or Firm-Lawrence 1. Field [22] Filed:

211 Appl. No; 319,118

Foreign Application Priority Data Dec. 30, 1971 Germany 266 38 utilized to line the passageway in said spout, a particui larly preferred material is melt-cast corundum.

[52] U.S. [51] Int.

[58] Field of Search 222/566, 567; 164/136, 10 Claims, 4 Drawing Figures WEAR-RESISTANT SPOUTS FOR METALLURGICAL VESSELS This invention relates to wear-resistant spouts for metallurgical vessels, in particular for tundish tuyeres and gate-nozzles, which must be endowed with very high resistance to wear with respect to steel melts.

The intermediate vessles of a continuous casting system, also called tundish, are provided with one or several bottom openings through which the liquid metal flows into the casting mold. When casting bars with large cross-sections, for instance slabs, the amounts of steel flowing from the tundish into the casting mold will be controlled by varying the flow cross-section, for instance by means of stopper rods or sliding shutters. When casting small cross-sections in continuous casting facilities for rods, such control is impossible on account of space limitations. In such cases the filling height in the tundish will be kept approximately constant so that the ferrostatic pressure remains approximately constant. Therefore the outflow rate of the melt into the casting mold will be determined by the crosssections of the outlets in the bottom, which generally are termed nozzles. Enlarging of the tundish nozzles cross-sections leads to an increase in casting rates of very adverse nature. This is so because continuous casting machinery allows changing the casting rates only within narrow limits. If the casting rates caused by increases in outflow nozzles widths exceed those limits, then casting time for one sequential casting, that is for uninterupted casting of several steel transfer ladles one after the other according to the state-of-the art so far .has been determined by the durability of the nozzles.

Panlike sliding shutters are advantageous not only for preheating the casting ladles but even more so as regards to their multiple applicabilities. Economical application is clearly improved on account of the repeated use of the same sliding shutter. The enlargement of the clear flow cross-section determines most of the time the frequency with which a sliding shutter may be used. The moment a given enlargement of the transmission channel has been reached, the sliding shutter must be replaced.

A number of proposals have already been made for solving the problem of better resistance to wear as regards the transmission channels in metallurgical vessels spouts. Thus it is known how to insert a replaceable wearing part for pan-like sliders. It consists of a qualitatively high grade fire-fast material of conventional ceramic manufacture or of metal-ceramic hard substances.

Essentially the solutions which have been proposed suffer from two drawbacks. The use of wear-resistant inserts of conventional, highly refractory materials or of metal-ceramic substances have been proposed. The refractory materials made in the usual ceramic manner possess total porosities of about percent or more. The metal-ceramic hard substances are less porous but also evidence a very high thermal conductivity and are expensive. These two drawbacks so far have prevented large scale applications.

The known proposals for wear-resistant transmission channels are too expensive as regards their construction to allow large-scale use. They are always provided with support devices so as to prevent slippage, even when a cement layer is provided. The simplest kind of self-stopping is an appropriate taper.

The present invention addresses itself to the task of developing a wear-resistant spout the cross-section of which will but slightly enlarge even after long times of casting and that furthermore may be mass-produced in simple manner.

Surprisingly, the solution to this problem was found in the use of practically pore-free, oxide-ceramic, refractory materials for the nozzle drain channels. According to the invention, melt-cast ceramic materials such as corundum and high-sintered, virtually pore-free oxide-ceramic refractory substances based on corundum, spinels, zirconium oxide, mullite and magnesite are particularly appropriate. It has been found that such pore-free ceramic materials obtained from a melt, which are endowed with high strengths but are of low resistance to temperature changes, may withstand without damage the temperature shock when the melt is first poured. Materials with porosities of less than 5 percent may be considered as being virtually pore-free.

The use of sleeves or of pipe sections inserted into the corresponding cross-sections of the spouts has particularly proved itself in practice where these conventional spouts had been enlarged. Such sleeves with wall thickness from approximately 2 mm to 10 mm may be easily and simply manufactured; for instance they may be bored out of melt-cast corundum blocks by means of conventional ceramic cements and into the appropriately prepared die components.

Spouts and nozzles may be manufactured as a whole from these virtually pore-free oxide-ceramic, refractory materials according to the invention. Furthermore, conically shaped or other blocking inserts may be made use of in a support body. Such inserts and spouts in practice have been found useful in special cases.

It was believed that the use of practically pore-free, oxide-ceramic materials was not feasible on account of their low resistance to temperature cycling. It is known that the temperature cycling resistance decreases appreciably with decreasing porosity for refractory products, and that cracks must be expected when there are shock-like temperature increases. The disadvantages of residual porosity in conventional ceramic materials and the slag penetrations related thereto are also known.

Therefore the prior art has turned to metal-ceramic substances, which are very pore-free and which are temperature-cycling resistant.

Comprehensive testing of the practically hermetic oxide-ceramic materials, for instance in the form of melt-corundum and of hermetically-pressed as well as high-sintered mullite and corundum substances, has surprisingly shown that although fine cracks may form occasionally under shock-like temperature loading, but that such fine cracks do not lead to deterioration of the wear-sleeves made of such pore-free substances and inserted into the spouts.

The invention will be explained in further detail in the description which follows and in drawings in which:

FIG. 1 is photograph of a used continuous-casting nozzle, made of various materials;

FIG. 2 is a side elevation showing a commerical, bored-out continuous-casting nozzle, which is cemented into a wear-resistant sleeve made from a meltcast corundum body, according to the invention;

FIG. 3 illustrates a slider arrangement, wherein a corundum sleeve is inserted into the bottom slide plate;

FIG. 4 illustrates another slider-shutter arrangement in which a continuous wear-resistant sleeve covering the joint between stone and plate is cemented following assembly of inflow body and bottom plate, and a continuous, wear-resistant sleeve covering the joint be tween stone and plate is cemented following assembly of outflow body and slider-plate.

FIG. 1 is a photograph of an used, experimental extrusion casting nozzle to 1:1 scale in which the nozzle holding body 30 consisted of a zirconium silicate, the upper part of inserted sleeve 31 consisted of meltcorundum and the lower sleeve part 32 consisted of a high-grade zirconium oxide of conventional ceramic manufacture. Residual slag remains in transmission channel 33, which will drain upon termination of casting. Initially the nozzle support body 30, made: of zirconium silicate, was about 30 mm longer. After operaof steel passed through this nozzle, body 30 is entirely eroded. Corundum sleeve.3l indicates a reaction range of about 1mm deep only at its contact area and elsewhere is free of any penetration. The lower sleeve part 32, which is made of high-grade zirconium oxide of conventional ceramic manufacture with a total porosity of about 17 percent exhibits strongpenetrations and clearly indicates appreciable wear. It must be observed in this respect that it is precisely in the lower range of the nozzle that normally the least wear is to be expected.

FIG. 2 shows a continuous-casting nozzle into which is cemented by means of cement layer 3, a melt-cast sleeve 2 made of corundum and bored-out. Fitting 4 of sleeve to the inflow funnel of the extrusion-casting may be effected either by finishing the corundum sleeve by means of diamond grinders or by means of an appropriate ceramic substance or cement, as shown in FIG. 2. Sleeve 2 may be kept from falling out by means of an outer cone or by appropriate ledges. The easily fashioned shape shown in FIG. 2 has proved to be reliable in practice as regards preventing slipping out. The wall thickness of the sleeve shown in FIG. 2 should exceed 2 mm. For the sake of simpler, mechanical manufacture, wall thicknesses ranging 5 to mm, preferably 8 mm, should be used. Such a sleeve also was made of melt-cast mullite and of the same dimensions, and in a further experiment, it consisted of a highly pore-free, sintered corundum tube section; the latters wall thickness was 3 mm.

Sleeves of appreciable wall thickness, from 5 mm upwards, may also be utilized as direct nozzles in lieu of nozzles with cemented sleeves, when inserted into an appropriate opening in the bottom of a tundish. Such nozzles are machined as a whole from melt-cast or from similar nearly pore-free, sintered ceramic materials in mechanical manner and their crosssectional contours preferably are round, although they may also be square or rectangular or hexagonal or polygonal. Viewed from above, the external shape of such nozzles, which might be made from melt-cast corundum stones, when sawed or bored out, are (preferably cylindrical) possibly with a flange, though most often without, or they. may be conical.

Continuous-casting nozzles, lined in accordance with the invention have been used for casting steel rods with square cross-section of an edge length of 180 mm. The steel composition was 0.08% carbon, 0.28% silicon, 0.5% managanese, 0.04% phosphorus, 0.03% sulfur and 0.006% aluminum. Casting was performed in two lines at rates of 1.8 to 2 meter/min. When making use of the conventional known nozzle materials such as zirconium silicate, zirconium oxide, mullite or other refractory materials containing residual contaminations up to about 5 percent or substantial amounts of clay, casting rates increased to above 2% meter/min after I hours, so that casting had to be interrupted. On the average, the clear transmission channel in the commercially conventional nozzle in the process had very unevenly enlarged from an initial diameter of 15 mm to approximately 17 to 20 mm. In part there were much more pronounced and also unilateral erosions requiring premature plugging of the nozzles. When making use of the nozzle of the invention, where the cemented sleeve consisted of melt-cast-corundum, the casting rates following figs of casting did not exceed 2 meter/min. The ID of the nozzle channel had been negligibly enlarged to about 16 mm.

The process of the invention for the economical manufacture of continuous-casting nozzles starts from the consideration that only a minor part of the nozzle will be attacked by the steel flowing through and by the slag particles that are carried along with the steel. According to the invention, more wear-resistant sleeves, preferably tubular sections, made of economical refractory materials such as fireclay, can be cemented into the nozzle bodies. These cemented die-bodies consist of materials with higher resistance to the melt flowing through the nozzle.

Nozzle body 1 consists of economical refractory material such as fireclay into which is cemented an appropriate tubular section 2 made of a more wear-resistant material such as zirconium oxide. Cement layer 3 consists of the same material as mentioned in the first example.

Such are preferably very finely ground materials with a high clay content and of grain size less than 0.3 mm, which are made into the proper consistency by means of adding the appropriate amount of monoaluminum phosphate or by means of adding the appropriate amount of water with clay melt elements. Also, cements made of MgO, signal (AL O MgO), zirconium oxide and zirconium silicate have been found practical.

als amounts to about 5:1 to 10:], while for large nozzles, the weight ratio will be more favorable. Preferably the conventional materials from the system Si0 -AlzO will be used as the economical nozzle mawhen manufacturing such insertion sleeves or tubular sections, where the required lengths will be sawed off, it was found that the relatively small wall thickness of these sleeve bodies from about 5 to mm will provide higher freedom from porosity of the refractory substance when making use of the conventional means.

The inner cross-sectional contours of the inserted, wearable nozzle components are not always circular. Oval and polygonal outflow cross-sections as well as crosslike and star-like cross-sections for quieting the casting jet have also been found useful.

The sense of the invention encompasses also lining the conventional pan-like outflows in whole or in part, for instance such as rings in the outflow range, with meltcast or hermetic, nearly pore-free sintered ceramic materials.

Such sleeves 15 for reducing wear in the bottom plate 13 and in slider plate 14 of pan-like slider shutters as shown in FIG. 3 have been found practical. Thus, for a 40 ton steel ladle, the time of replacement of the slider shutters could be raised from two to five castings by installing sleeves made of melt-cast corundum. One ring with a wall thickness of 10 mm was cemented into each of the plates of the bottom and of the slider. The plate material in that case consisted of economical quality with about 60% A1 0 content, while the plates of the comparison slider without sleeve consisted of a high grade material with about 85% A1 0 A further increase in time of operation of the slider shutters and by a factor of about two and in particular an appreciable improvement of operational reliability were surprisingly obtained by making use of continuous, wear-resistant sleeves l8 and 19, made for instance from melt-corundum, and installed over the inflow stone and bottom plate 21 as well as over slider plate 22 and outflow stone 23 as shown in FIG. 4. In this installation first the inflow stone 20 and the bottom plate 21 are installed by means of the customary assembly means and adjusting means into the ladle bottom. Following assembly, the ceramic sleeve 18 is cemented in. Obviously the inner bore into the inflow stone and into the bottom plate corresponding to the sleeve dimension must be made larger. Sleeve 19 is mounted into the assembled unit consisting of the slider plate 22 and outflow stone 23 in the sense of the invention. Assembling sleeves l8 and 19 together with the stoneand-plate assembly is also feasible and provides the same results. The joint between plate 21 or 22 and stone 20 or 23 will be avoided by means of the continuous, wear-resistant sleeves and therefore there will be no reinforced wear nor any steel penetration in the area of the joint.

Although the more wear-resistant sleeves in the die components such as bottom plates, slide plates, nozzles and drains were glued or cemented in the examples above, direct ceramic sintering of the wear-resistant insert with the die component has also been found practical when manufacturing large numbers of such components.

We claim:

1. A wear-resistant spout for metallurgical vessles, particularly a tundish nozzle and slider drain, consisting of a vessel provided with an orifice and a highly wearresistant insert in said orifice exposed to the melt, wherein the insert consists of a practically poreless oxide-ceramic refractory material.

2. A wear-resistant spout according to claim 1, wherein the insert consists of a practically poreless oxide-ceramic material that has been sintered at least at l,600C.

3. A wear-resistant spout according to claim 1, wherein the insert consists of a melt-cast oxideceramic.

4. A spout according to claim 1 wherein the insert in the vessel is maintained positively locked thereto.

5. A spout according to claim 1 wherein the insert is cemented into an orifice in the vessel.

6. A spout according to claim 1 wherein the insert and the vessel are sintered together.

7. A spout according to claim 1 wherein the insert is machined mechanically.

8. A spout according to claim 1 wherein the insert consists of corundum.

9. An insert according to claim 1 wherein the insert consists of mullite, magnesite, spinel, zirconium oxide individually or in combination.

10. A spout according to claim 1 wherein the insert consists of a double-part sleeve, of which one part is mounted in the bottom of the vessel and of which the other part is mounted in a slider shutter which selectively opens and closes the orifice in said vessel.

UN ITED STATES PA'EKINT ()FFMIE CERTEFICATE oF CORRECTION Patent No. 3,801,083 Dated April 2 197a Inventor(s) Paul Gerhard Mant ev Eberhard Knorr' It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Correct assignee to--Eisenwer=k-Gesellsshaft Maximilianshucte m.b .H

In the Abstract, line 1; correct--vessels-- Column 1, line 8; correct--vessels-- Column 4, line 16; correct--Al O MgO-- Signed and sealed this 1st day of October 1974.

(SEAL) Attest:

MCCOY M, GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents )RM Po-1050 (10-69) USCOMM-DC 60376-P69 A U. 5. GOVERNMENT PRINTING OFFICE I969 0-366-334, 

1. A wear-resistant spout for metallurgical vessles, particularly a tundish nozzle and slider drain, consisting of a vessel provided with an orifice and a highly wear-resistant insert in said orifice exposed to the melt, wherein the insert consists of a practically poreless oxide-ceramic refractory material.
 2. A wear-resistant spout according to claim 1, wherein the insert consists of a practically poreless oxide-ceramic material that has been sintered at least at 1,600*C.
 3. A wear-resistant spout according to claim 1, wherein the insert consists of a melt-cast oxide-ceramic.
 4. A spout according to claim 1 wherein the insert in the vessel is maintained positively locked thereto.
 5. A spout according to claim 1 wherein the insert is cemented into an orifice in the vessel.
 6. A spout according to claim 1 wherein the insert and the vessel are sintered together.
 7. A spout according to claim 1 wherein the insert is machined mechanically.
 8. A spout according to claim 1 wherein the insert consists of corundum.
 9. An insert according to claim 1 wherein the insert consists of mullite, magnesite, spinel, zirconium oxide individually or in combination.
 10. A spout according to claim 1 wherein the insert consists of a double-part sleeve, of which one part is mounted in the bottom of the vessel and of which the other part is mounted in a slider shutter which selectively opens and closes the orifice in said vessel. 